Generally, a device such as a mobile phone, a mobile information terminal, or the like has a display panel. A liquid crystal display device which includes a liquid crystal panel and a backlight that is an illuminating device is widely used for the display panel.
The liquid crystal panel and the backlight are fixed to each other through a sheet-shaped adhesive member attached to the frame of the backlight. The double-faced adhesive tape having a light blocking characteristic is mainly used for this adhesive member. Usually, the liquid crystal display device used for the mobile phone or the like has a structure in which no outer case (front chassis) is assembled to a display surface side of the liquid crystal panel. In this case, the liquid crystal panel and the backlight are fixed to each other through only the double-faced adhesive tape. An area of this double-faced adhesive tape is determined by an area of a non-display region of the liquid crystal panel. On the other hand, in recent years, the size of the liquid crystal display device has been reduced. Thus, the area of the non-display region tends to be reduced.
When the liquid crystal display device is installed in a portable device or the like and used, a flexible cable connecting the liquid crystal panel and a control board of the portable device is bent toward a side opposite to the display surface of the liquid crystal display device. At that time, a bending stress occurs in the flexible cable. Consequently, when a bonding strength of the double-faced adhesive tape through which the liquid crystal panel and the backlight are fixed to each other is low, there is a possibility in which the liquid crystal panel and the double-faced adhesive tape are separated from each other.
When the separation of the liquid crystal panel from the backlight occurs, the light from the backlight is not applied to the liquid crystal panel effectively. Accordingly, the display quality is lowered. In case that a touch panel for operating the mobile terminal or a protection panel for protecting the liquid crystal panel from being damaged is provided on the liquid crystal panel, these members contact with the liquid crystal panel. Accordingly, the display quality is further lowered.
FIG. 10 is an exploded perspective view of a display device described in Japanese Patent Application Laid-open Publication No. 2007-256467. FIG. 11 shows a shape of a protruding portion provided in the display device shown in FIG. 10. Specifically, when a circuit board 110 having flexibility shown in FIG. 10 is bent in a direction of a frame 300, the stress is applied to an adhesive sheet 120 with which a display panel 100 is bonded to a light guide plate 108. Consequently, a force is applied in a direction in which the display panel 100 is separated from the light guide plate 108. Here, the display device shown in FIG. 10 has a protruding portion 30 having a surface inclined to an outer surface of the display panel 100 on an inner surface of the frame 300. The protruding portion 30 presses the outer surface of the display panel 100 accommodated in the frame 300. Whereby, the display panel 100 is fixed to the frame 300. The protruding portion 30 is made of an elastic member. Accordingly, when the display panel 100 is accommodated in the frame 300, the display panel 100 is held by an elastic return force of the protruding portion 30.
As shown in FIG. 11A and FIG. 11B, the protruding portion 30 is provided on the inner surface of the frame 300 that faces the outer surface of the display panel 100 in the display device shown in FIG. 10. The protruding portion 30 has a surface inclined to the outer surface of the display panel 100 and is brought into contact with the outer surface of the display panel in a pressed state. In this case, the inner size of the frame 300 including the protruding portion 30 has to be smaller than the outer size of the display panel 100. The outer surface of the display panel 100 is brought into contact with the frame 300 during and after assembly to the frame 300.
A substrate used for the display panel 100 is made of mainly glass. Therefore, when the outer surface of the display panel 100 contacts with the frame 300, the member of the frame side is ground by a hard convexo-concave part of the end of the glass substrate and a foreign particle is generated. When the foreign particle is generated, the display quality is lowered.
The protruding portion 30 has to be made of the elastic member. Therefore, either a structure in which the whole frame 300 is made of the elastic member or a structure in which only the protruding portion 30 of the frame 300 is made of the elastic member has to be used. When the structure in which only the protruding portion 30 is made of the elastic member is used, the structure of the frame 300 becomes complex. As a result, easiness of assembling is lowered. On the other hand, when the structure in which the whole frame 300 is made of the elastic member is used, the strength of the frame may be reduced. Additionally, when the other member such as the touch panel or the like is attached to the frame 300, the other member may contact with the display panel. As a result, the display quality may be lowered.